Demagnetization protocols for frustrated interacting nanomagnet arrays

We report a study of demagnetization protocols for frustrated arrays of interacting single-domain permalloy nanomagnets by rotating the arrays in a changing magnetic field. The most effective demagnetization is achieved by not only stepping the field strength down while the sample is rotating, but also by combining each field step with alternation in the field direction. By contrast, linearly decreasing the field strength or stepping the field down without alternating the field direction leaves the arrays with a larger remanent magnetic moment. These results suggest that nonmonotonic variations in field magnitude around and below the coercive field are important for the demagnetization process. (C) 2007 American Institute of Physics.